1. Field of the Invention
The present invention relates to an object, a method, or a manufacturing method. In addition, the present invention relates to a process, a machine, manufacture, or a composition of matter. In particular, the present invention relates to, for example, a semiconductor device, a display device, a light-emitting device, a power storage device, a driving method thereof, or a manufacturing method thereof. In particular, the present invention relates to an oxide semiconductor film and a semiconductor device.
2. Description of the Related Art
Transistors used for most flat panel displays typified by a liquid crystal display device and a light-emitting display device are formed using an amorphous-based silicon semiconductor or a crystal-based silicon semiconductor silicon provided over glass substrates. Further, transistors formed using such silicon semiconductors are used in integrated circuits (ICs) and the like.
In recent years, attention has been drawn to a technique of using, instead of a silicon semiconductor, a metal oxide exhibiting semiconductor characteristics for transistors. Note that in this specification and the like, a metal oxide exhibiting semiconductor characteristics is referred to as an oxide semiconductor.
For example, a technique is disclosed in which a transistor is manufactured using zinc oxide or an In—Ga—Zn-based oxide as an oxide semiconductor and the transistor is used as a switching element or the like of a pixel of a display device (see Patent Documents 1 and 2).
Further, in Non-Patent Document 1, it has been reported that an amorphous In—Ga—Zn—O film has an extremely high defect level density of 1×1020/cm3 or higher and the number of defects is reduced by almost half by heat treatment.